1. Field of the Invention
The present invention relates generally to fluid delivery devices. More particularly, the invention concerns an improved apparatus for infusing medicinal agents into an ambulatory patient at specific rates over extended periods of time, which apparatus includes fluid flow indicator means and a novel adjustable flow rate control means for precisely adjustably controlling the rate of fluid flow from the reservoir of the device.
2. Discussion of the Prior Art
Many medicinal agents require an intravenous route for administration thus bypassing the digestive system and precluding degradation by the catalytic enzymes in the digestive tract and the liver. The use of more potent medications at elevated concentrations has also increased the need for accuracy in controlling the delivery of such drugs. The delivery device, while not an active pharmacologic agent, may enhance the activity of the drug by mediating its therapeutic effectiveness. Certain classes of new pharmacologic agents possess a very narrow range of therapeutic effectiveness, for instance, too small a dose results in no effect, while too great a dose results in toxic reaction.
In the past, prolonged infusion of fluids has generally been accomplished using gravity flow methods, which typically involve the use of intravenous administration sets and the familiar bottle suspended above the patient. Such methods are cumbersome, imprecise and require bed confinement of the patient. Periodic monitoring of the apparatus by the nurse or doctor is required to detect malfunctions of the infusion apparatus. Devices from which liquid is expelled from a relatively thick-walled bladder by internal stresses within the distended bladder are well-known in the prior art. Such bladder, or xe2x80x9cballoonxe2x80x9d type, devices are described in U.S. Pat. No. 3,469,578, issued to Bierman and in U.S. Pat. No. 4,318,400, issued to Perry. The devices of the aforementioned patents also disclose the use of fluid flow restrictors external of the bladder for regulating the rate of fluid flow from the bladder. The prior art bladder type infusion devices are not without drawbacks. Generally, because of the very nature of the bladder or xe2x80x9cballoonxe2x80x9d configuration, the devices are unwieldy and are difficult and expensive to manufacture and use. Further, the devices are somewhat unreliable and their fluid discharge rates are frequently imprecise.
The apparatus of the present invention overcomes many of the drawbacks of the prior art by eliminating the bladder and making use of recently developed elastomeric films and similar materials, which, in cooperation with a base define a fluid chamber that contains the fluid which is to be dispensed. The elastomeric film membrane controllably forces fluid within the chamber into fluid flow channels provided in the base.
The elastomeric film materials used in the apparatus of the present invention, as well as various alternate constructions of the apparatus, are described in detail in U.S. Pat. No. 5,205,820 issued to the present inventor. Therefore, U.S. Pat. No. 5,205,820 is hereby incorporated by reference in its entirety as though fully set forth herein. Co-pending U.S. Ser. No. 08/768,663 filed by the present inventors on Dec. 18, 1996 also describes various alternate constructions and modified physical embodiments of the invention. Because the present application discloses improvements to the apparatus described in U.S. Ser. No. 08/768,663, this co-pending application is also hereby incorporated by reference in its entirety as though fully set forth herein. U.S. Pat. No. 5,721,382 issued to the present inventor on Feb. 24, 1998 discloses an apparatus for indicating fluid pressure within a conduit. The present invention comprises an improvement to the devices disclosed in this latter patent and, therefore, U.S. Pat. No. 5,721,382 is also incorporated by reference as though fully set forth herein.
The apparatus of the present invention can be used with minimal professional assistance in an alternate health care environment, such as the home. By way of example, devices of the invention can be comfortably and conveniently removably affixed to the patient""s body and can be used for the continuous infusion of antibiotics, hormones, steroids, blood clotting agents, analgesics, and like medicinal agents. Similarly, the devices can be used for I-V chemotherapy and can accurately deliver fluids to the patient in precisely the correct quantities and at extended microfusion rates over time.
The embodiments of the invention described in U.S. Ser. No. 08/768,663, which application is incorporated herein by reference, comprises a fluid delivery apparatus having a fluid reservoir and an indicator assembly for indicating fluid flow through the apparatus. However, the apparatus of the present invention, also includes a unique, adjustable fluid flow rate mechanism which enables the fluid contained within the reservoir of the device to be precisely dispensed at various selected rates. As will be better understood from the description which follows, the novel adjustable fluid flow rate control mechanism of the present invention includes locking means which is operable only by a physician or health care worker who is in possession of a physician operating key. Accordingly, once a particular flow rate is selected, the patient cannot unilaterally change the flow rate.
It is an object of the present invention to provide an apparatus for expelling fluids at a precisely controlled rate which is of a compact, low profile, laminate construction. More particularly, it is an object of the invention to provide such an apparatus which can be used for the precise infusion of pharmaceutical fluids to an ambulatory patient at controlled rates over extended periods of time.
It is another object of the invention to provide an apparatus of the aforementioned character which is highly reliable and easy-to-use by lay persons in a non-hospital environment.
Another object of the invention is to provide an apparatus which can be factory prefilled with a wide variety of medicinal fluids or one which can readily be filled in the field shortly prior to use.
A further object of the invention is to provide a low profile, fluid delivery device of laminate construction which can be manufactured inexpensively in large volume by automated machinery.
Another object of the invention is to provide a device of the aforementioned character which includes novel adjustable flow rate control means disposed intermediate the fluid reservoir outlet and the outlet port of the device for precisely controlling the rate of fluid flow from the outlet port toward the patient.
Another object of the invention is to provide a device of the character described which embodies a highly novel fluid flow indicator that provides a readily discernible visual indication of fluid flow status through the device.
Another object of the invention is to provide an apparatus of the aforementioned character in which the stored energy source is of a novel laminate construction which can be precisely tailored to deliver fluid from the device at precise rates.
Another object of the invention is to provide unique fill means for use in controllably filling the fluid reservoir of the apparatus.
Another object of the present invention is to provide an apparatus of the aforementioned character in which the flow rate control means comprises a rotatable flow restrictor support disk that can be rotated by the treating physician to selectively position the flow restrictor between the fluid reservoir and the device outlet port.
Another object of the present invention is to provide a flow rate control means of the type described in the preceding paragraph in which the flow restrictors comprise porous frits of varying porosity.
Another object of the present invention is to provide a flow rate control means in which the flow restrictors comprise wafers which have been laser drilled to provide a plurality of micro bores of various sizes.
Another object of the invention is to provide an apparatus as described in the preceding paragraphs which includes locking means for locking the variable flow rate control disk in a preset position so that the rate control can be set only by the treating physician or an authorized health care worker having an operating key.
Another object of the invention is to provide a novel fill assembly for use in filling the fluid reservoir of the apparatus of the invention.
By way of summary, the improved fluid delivery apparatus of the present form of the invention comprises three major cooperating subassemblies, namely a reservoir subassembly, a highly novel adjustable, key-operated fluid flow rate control subassembly and a flow indicator subassembly for visually indicating fluid flow through the device. The reservoir subassembly, which readily lends itself to automated manufacture, is generally similar to that described in copending U.S. Ser. No. 08/768,663 and includes a base and a stored energy means comprising at least one distendable elastomeric membrane which cooperates with the base to form a fluid reservoir. The fluid flow indicator subassembly is also somewhat similar to that described in U.S. Ser. No. 08/768,663 and comprises a mechanical fluid flow indicator that provides a clear visual indication of normal fluid flow and absence of fluid flow either because the reservoir is empty or because the flow lines are occluded. Additionally, the apparatus of the invention includes fill means for use in filling the reservoir of the reservoir subassembly this fill means here comprises a fill assembly which can be mated with the base of the reservoir subassembly for use in controllably filling the reservoir thereof.